Study of the Efficacy, Safety, and Tolerability of Serlopitant for the Treatment of Refractory Chronic Cough

Inclusion Criteria: * Female and males between 18 and 80 years of age * Have a diagnosis of treatment refractory chronic cough or unexplained cough for at least one year * Chest radiograph or computed tomography (CT) Thorax within the last 5 years not demonstrating any abnormality considered to be significantly contributing to the chronic cough * At Screening have a score of ≥ 40mm on the Cough Severity VAS * At Baseline (Day 0) have a score of ≥ 40mm on the Cough Severity VAS * All female subjects who are of childbearing potential must practice highly effective contraception (i.e., pregnancy prevention method with a failure rate of \< 1% per year) from the time of the initial screening visit until 4 weeks after last dose of study drug. Please refer to the protocol for acceptable methods of contraception Exclusion Criteria: * Prior treatment with serlopitant or other NK1-R antagonist * Presence of any medical condition or disability that could interfere with study * History of hypersensitivity to serlopitant or any of its components * Currently pregnant or male partner of pregnant female * Females of childbearing potential who are unable or unwilling to use adequate contraception or who are breast feeding * Current smoker or individuals who have given up smoking within the past 12 months * FEV1/FVC \< 60% * Body mass index (BMI) \<18 kg/m2 or ≥ 40 kg/m2 at Screening * History of upper or lower respiratory tract infection or recent significant change in pulmonary status within 4 weeks of the Baseline Visit (Day 0) * History of cystic fibrosis * History of opioid use within 1 week of the Baseline Visit (Day 0) * Requiring concomitant therapy with prohibited medications * Treatment with biologic therapies within 8 weeks or 5 half-lives prior to the Baseline Visit (Day 0), whichever is longer * Treatment with strong CYP3A4 inhibitors within 4 weeks prior to the Baseline Visit (Day 0) * Treatment with any investigational therapy within 4 weeks (investigational biologic therapies within 8 weeks) prior to the Baseline Visit (Day 0) * Serum creatinine, total bilirubin, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 2x the upper limit of normal (ULN) during screening * Positive test for any drug of abuse * History of malignancy within 5 years prior to the Baseline Visit (Day 0), with the exception of completely treated and non-metastatic basal cell carcinoma or squamous cell carcinoma of the skin * Any known psychiatric diagnosis meeting DSM-5 criteria which may confound the assessment of serlopitant safety or efficacy, or interfere with the subject's ability to comply with protocol-mandated activities, within 3 years prior to randomization. Examples of such DSM-5 diagnoses include but are not limited to major depressive disorder, bipolar disorder, schizophrenia, psychotic disorder, intellectual disability, severe alcohol use disorder. * Known active hepatitis infection * Known history of human immunodeficiency virus (HIV) infection